The Canadian
Forest Fire Weather Index (FWI) System

The Canadian Forest
Fire Weather Index (FWI) System consists of six components that account
for the effects of fuel moisture and wind on fire behavior. The first
three components are fuel moisture codes and are numerical ratings of
the moisture content of litter and other fine fuels, the average moisture
content of loosely compacted organic layers of moderate depth, and the
average moisture content of deep, compact organic layers. The remaining
three components are fire behavior indexes which represent the rate of
fire spread, the fuel available for combustion, and the frontal fire intensity;
their values rise as the fire danger
increases. Calculation of the components is based on consecutive daily
observations of temperature, relative humidity, wind speed and 24-hour
rainfall. The six standard components provide numerical ratings of
relative wildland fire potential.